The present invention relates to an organic luminescence device having an organic luminescence lamination structure including a fluorescent organic compound layer sandwiched between an anode and a cathode, particularly to an organic luminescence device exhibiting stable luminescence characteristics for a long period of time.
An organic luminescence device generally comprises a pair of an anode (electrode) and a cathode (electrode), and an organic thin film (layer) comprising a fluorescent organic compound disposed between the anode and the cathode. In the organic luminescence device, electrons and holes are injected form the respective electrodes into the fluorescent organic compound layer to generate excitons of the fluorescent organic compound, and the resultant excitons are returned to the ground state to cause luminescence (emission of light). By appropriately changing an organic fluorescent dye, it becomes possible to allow a latitude in conversion of emitted light. Further, the organic luminescence device is a self-emission device, thus exhibiting excellent performances such as a good visibility. As a result, the organic luminescence device is expected to be used as displays for portable or hand-held data terminals and various industrial equipment.
However, the organic luminescence device has been accompanied with such a difficulty that luminescence characteristics are remarkably lowered when the organic luminescence device is driven for a long period of time.
One of factors causing such a lowering in luminescence characteristics may include moisture (or water content) contained within the organic luminescence device. More specifically, moisture present within organic materials used in the organic luminescence device or moisture permeating or entering the organic luminescence device causes peeling-off of a cathode metal material layer, thus resulting in dark spots being defective stops causing electrical conduction failure.
Accordingly, it is necessary to remove moisture present within the organic luminescence device in order to suppress an occurrence of dark spots.
For this purpose, several proposals have been made.
More specifically, Japanese Laid-Open Patent Application (JP-A) 7-169567 discloses an organic luminescence device having a lamination structure comprising a device including an anode, an organic luminescence material layer and a cathode; a protective film containing a drying agent disposed outside the device; and a sealing layer disposed on the protective film.
JP-A 3-261091 disclose an organic luminescence device having a hermetic sealing casing having a sealed hollow space including therein a lamination structure and drying means, wherein the lamination structure comprises a pair of opposing electrodes and an organic luminescence material layer sandwiched between the electrodes, and the drying means comprises phosphorus pentoxide and is disposed apart from the lamination structure in the sealed hollow space.
Further, JP-A 9-148066 discloses an organic luminescence device having a hermetic sealing casing similar to that described in JP-A 3-261091 except for using a drying agent comprising an alkali earth metal oxide (in place of phosphorus pentoxide).
However, the above-mentioned conventional organic luminescence devices have been accompanied with the following problems. Specifically, in the organic luminescence device disclosed in JP-A 7-169567, the cathode is liable to be damaged by formation of the protective film. In the organic luminescence device disclosed in JP-A 3-261091, an adverse influence of phosphoric acid derived from phosphorus pentoxide and moisture has been pointed out. Further, the organic luminescence device disclosed in JP-A 9-148066 involves a toxic effect of some species of metal oxide. (BaO in this case)
A principal object of the present invention is to provide an organic luminescence device having solved the above-mentioned problems of the conventional organic luminescence devices.
A specific object of the present invention is to provide an organic luminescence device using a drying agent free from an adverse influence on the organic luminescence device and free from toxicity thereby to maintain stable luminescence characteristics for a long period of time and allow a safe organic luminescence device.
According to the present invention, there is provided an organic luminescence device, comprising:
an organic luminescence lamination structure comprising a pair of an anode and a cathode, and at least one organic compound layer disposed between the anode and the cathode,
a hermetic sealing housing enclosing therein the organic luminescence lamination structure and blocking external air, and
a drying agent disposed within the hermetic sealing housing, wherein
the drying agent comprises a compound represented by the following formula (1):
Rxe2x80x94NCOxe2x80x83xe2x80x83(1),
wherein R denotes a substituted or unsubstituted alkenyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted styryl group, a substituted or unsubstituted acyl group, or a substituted or unsubstituted heterocyclic group.
In the organic luminescence device, the drying agent of the formula (1) may be in a polymerized form or may comprise a mixture comprising the compound of the formula (1), preferably in a polymerized form, and an inorganic compound. Further, in a preferred embodiment, the compound of the formula (1) as the drying agent may be formed on the organic luminescence lamination structure by vacuum (vapor) deposition or coating.
These and other objects, features and advantages of the present invention will become more apparent upon a consideration of the following description of the preferred embodiments of the present invention taken in conjunction with the accompanying drawings.